C.J. Larson No.1 Reservoir Report
Nearby: Joe Gesinger No.1 H. Lesmeister
Last Updated: December 13, 2025
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Summary
Larson No.1 is a privately owned dam located in Dewey, South Dakota, along the TR MOREAU river, constructed in 1945. This earth dam stands at a height of 22 feet and spans a length of 600 feet, with a storage capacity of 128 acre-feet. The dam is regulated by the South Dakota Department of Environment and Natural Resources (DENR) and undergoes regular state inspections, enforcement, and permitting processes to ensure its safety and compliance with regulations.
Despite its low hazard potential and current "Not Rated" condition assessment, C.J. Larson No.1 plays a crucial role in water resource management in the area, providing flood control and storage capacity for the surrounding region. The dam has a normal storage capacity of 50 acre-feet and a maximum discharge rate of 360 cubic feet per second. While the dam does not have an Emergency Action Plan (EAP) in place or updated contact information, it continues to be a significant infrastructure for water resource enthusiasts and climate advocates in the region.
Overall, C.J. Larson No.1 serves as a key feature in the St. Paul District of South Dakota, contributing to the management of water resources along the TR MOREAU river. With its historical significance dating back to 1945, this earth dam remains an essential component of the local water infrastructure, highlighting the importance of continued monitoring, maintenance, and regulatory oversight to ensure its long-term functionality and safety for the community and the environment.
Year Completed |
1945 |
Dam Length |
600 |
Dam Height |
22 |
River Or Stream |
TR MOREAU |
Primary Dam Type |
Earth |
Hydraulic Height |
22 |
Nid Storage |
128 |
Hazard Potential |
Low |
Nid Height |
22 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Moreau R Near Whitehorse Sd
|
35cfs |
Grand R At Little Eagle Sd
|
47cfs |
Oak Cr Near Wakpala Sd
|
10cfs |
Bad R Near Fort Pierre Sd
|
7cfs |
Dam Data Reference
Condition Assessment
SatisfactoryNo existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.
Hazard Potential Classification
HighDams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.
C.J. Larson No.1